--> Production Potential Evaluation of Tectonically Enhanced Fracture Systems from Electrical Images, by J. Cadenhead, M. Grace, and B. Newberry; #90986 (1994).

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Abstract: Production Potential Evaluation of Tectonically Enhanced Fracture Systems from Electrical Images

John Cadenhead, Mike Grace, Bill Newberry

Naturally fractured reservoirs are an important, but challenging, exploration objective. Fracture aperture and density are the controlling parameters for initial production. The effect of folds and fault flexures can greatly enhance and preserve fracture widths and frequency. A variety of logging techniques including resistivity, acoustic, and nuclear measurements have been used to locate and orient fracture systems. However, the only reliable method for in situ fracture aperture measurement is from borehole electrical images. A variety of productive wells were included in a study to compare actual production to fracture apertures. The results are consistent with accepted theory of a cubic relation between flow potential and fracture apertures. Each field studied exhibited the same in tial production versus fracture aperture profile. Minimum apertures for commercial production have been established for different types of hydrocarbons. An electrical image derived 0.1 mm. aperture is the minimum for oil production and 0.05 mm. is the minimum for gas production. A very accurate production prediction can be established for a field when one or two wells are incorporated to provide points along the production prediction curve. Then, the varying conditions of viscosity, pressure, and relative permeabilities can be normalized. After the fracture apertures are calculated, the highest apertures are oriented to the structural position of the borehole. This is used to determine the optimum trajectory for deviated boreholes to maximize the penetration of the highest fracture apert res. These were observed in our field studies to be aligned with the axis of folds. The case studies presented are from vertical and horizontal boreholes in synclines, meteor craters, and in the distorted sections which surround both normal and reverse faults.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994